Best Free Antivirus Software

Introduction

To begin with let me say this: there is no best antivirus out there. Why do I say this? Any product that you take will behave differently against various virus samples since the AV engines and other components incorporated in them are of different technologies.

While one product might have higher detection ratio, another might have better malicious URL blocking or virtualization techniques, yet another might have lesser impact on system performance and so on.

Read more about Antivirus Engine and other related details at the end of this article.

Antivirus Engine

It is used for Real Time malware protection of files and is the core component to scan data on your PC for detecting and removing malware from hard disk, memory, boot sectors, network drives, removable disks, or from external network traffic (internet).

How does an antivirus detect malware:

Firstly you got the signature-based detection which contains an offline database of known patterns of malware downloaded from the internet which can identify specific malware codes or family of malware. Then you have heuristic based detection that identifies pieces of code that are unlikely to be found in legitimate programs and hence is prone to false positives depending on the sensitivity of heuristics. Virtualization and sandboxing unpacks or executes unknown programs in an isolated secure environment so that their behaviour can be analysed and scanned using the antivirus engine. The latest one is cloud based detection that requires a reliable internet connection and sends the suspicious scanned file over the internet and the analysis is done by the vendors' machine running the cloud engine.

Scanning for viruses:

Most antiviruses include these basic scan types: On-demand scan/manual scan is initiated by the user from right click context menu or from within the software. On-access scan is initiated when the resource is being accessed like running an executable, copying files from external drives etc. Scheduled scan periodically ensures that the system is free from malware by setting the time and frequency for scanning. Startup scan/quick scan checks most important locations like running processes, startup items, system memory and services, boot sectors and so on.

To be Continued in the next update....... Firewall, Proactive protection, Web protection components and more.

Editor

This software category is maintained by volunteer editor George.J. Registered members can contact the editor with any comments or questions they might have by clicking here.

I tried using BitDefender, another highly recommended program by PCMag.com. It kept causing Thunderbird email to hang, with the "not responding" message. Every time I sent an email, it would stall for 2-3 minutes.

Maybe Qihoo 360 Total Security is a good software, but I have some complains. When one searches for files to clean-up, the program might indicate 20Gb to clean up. You do the cleanup and afterwards search again: the same value is displayed, which sounds weird to me. If for some reason, some files can not be cleaned up, fear enough, but then say so or do not put them in the clean-up list.

Kaspersky and BitDefender are consistently the highest rated antivirus softwares, year after year. So I jumped at this opportunity. One day later, I've uninstalled Kaspersky.
Why? When browsing the internet, I kept getting popups "Attention! Your confirmation is required to perform the selected action. This action will reduce the protection of your computer." And when I say "OK" to that one, another one pops up with a warning about the certficate for that website.
These are websites that I visit regularly with no problem.
Plus: there are a dozen or more notifications sent to the Windows Action Center every day.
The whole thing is just a big pain to deal with.

Thank you for the feedback. I do not plan to install it on my main system, but I might on my secondary laptop, to try it out. But from what you describe, it will be a pain to encounter such messages on even good sites. Maybe you can whitelist those sites somewhere?
I was thinking of installing it on computers of my friends and relatives, since it seems like a good option. Maybe for us experienced users, these messages may be a bit of a pain to deal with, but for inexperienced ones, these might be helpful.
It will be available in India in September, so I can try it only then.

I installed this earlier in the week. Seems to be fine. Light on resources and not difficult to use.
(Had happily been using Avast until now)!
One point though:
In SETTINGS / ADDITIONAL / THREATS and EXCLUSIONS - I have deactivated the "ADVANCED DISINFECTION",
this as this function will use "considerable computer resources"!!!
I prefer to have an Anti-Virus solution that is as LIGHT as possible!
Besides this...seems to be working perfectly.

360 Total Security is a decent program although too bloated for my tastes like most of the leading commercial programs.
I prefer Bitdefender AV 2017 Free in conjunction with their separate free Anti-ransomware app.
Industry leading protection in all independent testing and very light on resources.
Very minimalist interface with virtually no input required from the user plus it was rated by the CIA's hackers as the most difficult AV to penetrate (in fact they could not hack computers protected by BD according to the Wikileaks recent release of internal CIA secret documents) and the free version uses the same scan engine and technology as their paid versions according to tests done by Neil Rubenking.
Most of the free AV program available these days are good and I guess it is more a question of meeting the needs and expectations of individual users.

For Windows 10 users the latest Bitdefender Free AV coupled with their stand alone BD Anti-Ransomware which is also free offers excellent protection.
Same highest rating results as their commercial product but very lightweight, unobtrusive and free. Not configurable which won't please the geeks but a great option for the average user in my opinion.
The latest version of Bitdefender AV Free will only work with Windows 7 Service Pack 1 through to Windows 10.

Strange. It used to use only 60MB when I had a resident antivirus running on my system. And around 80-90MB with Bitdefender and Avira engines enabled out of the total 8GB RAM available. I don't recommend running the Essentials version [TSE] because it's slow to update [still at v8 compared to v9 for TS] and doesn't get all the fixes that Total Security [TS] gets. I haven't tested on Windows 7 though as all these results are from Windows 10.

I am trying to install BitDefender Free
Their 2016 version won't install in XP (or Vista)
I have nearly gone insane attempting to get their FREE XP version (it is the 2015 version)
I managed to get a link (to the 2015 version) from the 2016 failed install.
But I cannot work out whether if that is their free version.
Can anyone point me to the free XP version ?

From the product website: - "Operating system: Windows 7 Service Pack 1, Windows 8, Windows 8.1, Windows 10". Some free solutions such as Avast do still work on XP although protection will be limited at best considering XP is now obsolete and system vulnerabilities are no longer patched. MC - Site Manager.

I find it my self very similar as you described in your reviews. 360 is the best, Comodo has improved a lot in the last years, Avira always been good. But I find it confusing why Quihoo's 360 is not represented in the big AV-Comparatives? Neither Comodo... I recommend you one more antivirus to review: Sophos Home. Is the third biggest security company on the world (behind Norton and Kaspersky), light on resources (cloud), very simple to use and in quite a few tests (Scanning speed, resource management, total hits, etc...) is in the top of the AV softwares.

Qihoo 360 was removed from av-comparative, AV-TEST and Virus Bulletin because they were cheating. You can googled for the news. I'm going to share the link, but when trying to post my comment, it was blocked.

I've tried Sophos Home recently and I am not yet convinced of using it beyond my tests. Detection can be very good but on AV Comparatives it's overall real world detection is similar to Windows Defender, sometimes worse! For resources, on my PC it has 6-8 various components which when idle total around 300mB of RAM, that's a lot and although I have 8GB RAM the PC feels a bit sluggish especially when browsing. It's also a pain having to go into the online control panel to add exceptions and other tasks rather than doing it immediately and smoothly in the client software.

Also re-tried Avira recently. I found it's heuristics to be really excellent, unlike the review above, especially on identifying macro viruses and trojan downloaders which then download Locky and other ransomewhere. In my tests Avira detected all zero day stuff that had just arrived in my mailbox and this was confirmed as brand new on Virustotal and with Avra being in the first bunch of 7-10 detectors out of 55 that quickly, even immediately detected these things. On the downside, once detected, cleanup is very slow which would not be a problem but it leaves lots of remnant files and folders which is confusing and makes the user think that the malware is still there. Also the interface is not only very old but also quite confusing. The seperate program / process of Luke Filewalker is just plain ridiculous in my view, it should be integrated fully and seamless.

Tried most others but currently still on Windows Defender because it has the least impact and the best cleanup but detection although much improved this year needs to be a lot higher.

The latest beta of free Bitdefender looks promising but whilst it remains a beta I won't be trying it.

Avira has not been compatible with XP for more than two years - https://www.avira.com/en/support-for-home-knowledgebase-detail/kbid/1752 .

For those still running XP (and which should be utilizing the Registry hack to enable receiving the WEPOS updates - http://www.ghacks.net/2014/05/24/get-security-updates-windows-xp-april-2019/), Bitdefender Free is a lightweight solution that has demonstrated adequate protection on the several machines that I have had it installed on.

When I upgraded to W10 Pro, I was prepared to give Windows Defender a try.
My PC is not powerful, and when I noticed it getting sluggish sometimes, I checked and Win Defender was busily scanning my drive (even inside zip files) when no scan had been scheduled or requested.
I like to control what is happening, and when, so Windows Defender is gone.

Qihoo 360 Total Security light? Not here. RAM usage for all processes averages around 70MB (balanced mode, without Avira and Bitdefender engines) compared with around 15MB for my previous AV, Panda Free. 360 TS is far too bloated. Also, less experienced users need to be very wary of what's being deleted/changed if they use any of the optimization tools. Certainly not recommended by me.

Click on the Protection tab in the Left side bar of the UI and then click on Custom settings. Scroll down and enable any of the engines you like and press OK. Now go to Virus scan tab in the left side bar, and then on the bottom move the slider bar to green over the Avira/Bitdefender engines.

If it was me I would enable them only during on-demand scans, and disable it in real-time.

It's important to note that idle RAM usage is not the only parameter to check if a software is light or not. How an antivirus affects application launches, installing/uninstalling softwares, boot time, archiving and extracting, file copying, downloading from web browsers, processor and ram usage when idle and during scans/updates along with various other factors determine the performance impact of an antivirus.

On a lighter note, Qihoo 360 usually took only around 30MB for me on idle without additional engines. What we can infer from this is that system configuration also plays an important role on the same. Additionally using any optimization software involves some knowledge about the same, but Qihoo's own tools are pretty safe to use and doesn't involve registry cleaning or advanced optimization techniques. But I wouldn't still recommend 360 TSE (Essentials) over 360 TS because it has slower updates and sometimes more false positives for some reason.

Thanks for the quick reply. Reading other glowing reviews and user experiences of 360 TS it does seem I'm in the minority regarding RAM usage. I was wondering if there was a conflict with Zemana AntiLogger Free as 360 TS also has an anti keylogger component but disabling ZAL made very little difference. I'll persevere with 360 TS though because fundamentally it seems pretty good.

I'm not sure how much I trust Qihoo and their products after reading how easily they got duped into whitelisting malware (http://www.securityweek.com/cybercriminals-trick-qihoo-360-whitelisting-malware). Not only that, but the article goes on to point out that "Testing bodies AV Comparatives, AV-TEST and Virus Bulletin decided to revoke all certifications and rankings awarded to Qihoo 360 products last year after they found that the products submitted for testing behaved differently from ones offered to customers."

Thanks for posting the article as well as bringing that to my attention. Qihoo should have double checked the products before whitelisting them.
About the revoking of certifications, that's definitely between them and the testing bodies. But when Qihoo 360 TS already does splendidly well with the default configuration that I tested (rather than the modified version submitted to testing bodies) there's little for me to complain about here. But like MC has mentioned before, using software's in their default configuration is unacceptable unless you want to go through the "easy" route. Many users customize the product according to their tastes and hence the level of protection/usability/performance varies according to each configuration.
Hence testing products in their default configuration is not exactly the right way to do. It just seems simpler.